Preparation of paper pulp



Patented Nov. 16, 193? PATENT, OFFICE 2,099,400 PREPARATION OF PAPER- PULP Edwin P. Jones, Garden City, N. Y., assignor to Champagne Paper Corporation, New York, N. Y., a corporation of New York No Drawing. Application October 19, 1936, Serial No. 106,369

2 Claims. (01, 92-16) The present invention relates to theproduction of a high grade bleached pulp or paper stock from fiax or hemp tow.

Flax or hemp tow is now produced by a num- 5 ber of known chemical and/or mechanical methods or may be produced in a special decorticator. As thus produced, the tow contains approximately from 50% to 60% bast fibers, and this tow is used as the raw material from which I produce a high grade bleached pulp or paper stock' by the improved method of my present invention. As the nature of the flax or hemp straw from which the tow is .produced and the chemical and/or mechanical means employed to free the same of a part of the woody matter, determines the ultimate character of the tow, the process or method employed by me in producing therefrom a high grade bleached pulp or high grade paper stock must of necessity be flexible in the method 20 of treatment of the tow and the kind and amount of chemicals utilized in practicing the process or method. For example, if the tow contains, say,

approximately 50% best fiber, the steps of the method or process employed if the tow contains 25 as high as, for example, 80%, bast fiber, will differ specifically in minor details. Therefore while my process or method as disclosed in the present application is generic as far as the treatment of tow to produce therefrom a high grade pulp, yet 30 the specific steps and particularly the specific quantities of chemical materials employed will of necessity vary with the character of the base material.

In carrying out my present invention-the tow 35 containing from approximately 50% to80% bast fibers is preferably immersed in water for a sufficient time to dissolve water soluble ingredients.

The tow may be taken in the wet state and placed in a digester of conventional design, pref- 40 erably a rotary digester, and cooked while being rotated under the following conditions:

(1) The amount of water used in the digester may vary between approximately 2 to 4 times the dry weight of the fiber;

45 (2) The temperature during the cooking may vary from between approximately 135 and 165 centigrade, the temperature corresponding to a gauge pressure between approximately 30 and 85 pounds per square inch; 9

50 (3) The cooking time in the digester may vary between 5 to 8 hours;

(4) To the mixture of water and fiber in the digester chemicals are used constituted of a mixture of sodium hydroxide and sulphur, it being 65 understood thatthe' percentage of the chemicals employed has reference tothe percentage of the chemicals as based upon the dry weight of the fiber under treatment.

The chemicals employed are utilized in the following proportions based upon the dry weight 5 of the fibers under treatment:

Percent Sodium hydroxide 14 to 20 Sulphu.1" 1 to 4 After the. digesting operation has been completed,'the digester is blown and the digested fiber is washed to remove the excess shive fiber as well as to remove the impurities in the fiber which have been rendered water soluble by the 15 digesting process.

The washed fiber may now be suitably treated to place the pulp in a dry or semi-dry condition for storage or may be directly subjected to a bleaching process, preferably a two stage bleaching process in such a manner as to produce varying amountsof oxycellulose or related compounds, as such oxycellulose or related com: pounds impart special desirable properties to the paper made from the bleached pulp.

The process or method as above described produces a high grade bleached pulp from which an extremely high grade of paper may be manufactured, and in which paper there is a minimum of shives and also in which'such shives as are present are invisible and which do not materially affect the grade of the paper. e

The proportion of the chemicals employed are selected in accordance with the proportional content of shives in the fiax tow treated.

Whereas I have described my invention by reference to specific forms thereof, it will be understood that many changes and modifications may be made without departing from the spirit of the invention. 40

I claim:

1. That improved method of producingbleached pulp from fiax or hemp tow, which consists in subjecting the tow to a cooking operation in a digester with a solution of water of approximately 2%; to 4 times. the dry weight of the fiber, and 14% to 20% sodium hydroxide and 1% to 4% sulphur, the quantities of the chemicals employed in the solution being based on the dry weight of tow; then washing the cooked fiber to remove 0 shive fiber and water soluble impurities, and bleaching the'fiber.

2. That improved methodof producing bleached pulp from fiax or hemp tow, which con.-

sists in dissolving water soluble materials by immersing the tow in water; then subjecting the tion being based on the dry weight of .tow; then tow to a. cooking operation in a digester with a Washing the cooked fiber to remove shive fiber solution of water of approximately 2 to 4 times and water soluble impurities, and bleaching the the dry Weight of the fiber, and 14% to 20% fiber.

sodium hydroxide and 1% to 4% sulphun-the v EDWIN P. JONES. quantities of the chemicals employed in the solu- 

